1. Field of the Invention
The present invention relates to a magnetic detection element including a pinned magnetic layer in which the magnetization direction is pinned and a free magnetic layer which is disposed on the above-described pinned magnetic layer with a non-magnetic material layer therebetween and in which the magnetization direction is varied due to an external magnetic field. In particular, it relates to a magnetic detection element capable of maintaining the product ΔRA of a variation of magnetoresistance ΔR and an element area A at a high level and reducing the magnetostriction of the free magnetic layer, as well as a method for manufacturing the same.
2. Description of the Related Art
FIG. 7 is a partial sectional view of a known magnetic detection element (spin-valve type thin film element) cut along a direction parallel to a surface facing a recording medium.
In FIG. 7, reference numeral 1 denotes a substrate layer formed from Ta. A seed layer 2 formed from a metal, e.g., Cr, having a body-centered cubic structure (bcc structure) is disposed on this substrate layer 1.
A multilayer film T1, in which an antiferromagnetic layer 3, a pinned magnetic layer 4, a non-magnetic material layer 5, a free magnetic layer 6, and a protective layer 7 are laminated sequentially, is disposed on the seed layer 2.
The protective layer 7 is formed from Ta, the non-magnetic material layer 5 is formed from Cu, the free magnetic layer 6 and the pinned magnetic layer 4 are formed from a Heusler alloy, e.g., CO2MnGe, and the antiferromagnetic layer 3 is formed from PtMn.
Electrode layers 10 and 10 are disposed on the top and the bottom of the multilayer film T1, and a direct current serving as a sense current is flowed in a direction perpendicular to the film surface of the multilayer film.
An exchange coupling magnetic field is generated at the interface between the antiferromagnetic layer 3 and the pinned magnetic layer 5, and the magnetization of the above-described pinned magnetic layer 5 is pinned in a height direction (Y direction shown in the drawing).
Hard bias layers 8 formed from a hard magnetic material, e.g., CoPt, are disposed on both sides of the free magnetic layer 6, and the top, the bottom, and the end portions of the hard bias layers 8 are insulated by insulating layers 9. The magnetization of the free magnetic layer 6 is aligned in a track-width direction (X direction shown in the drawing) by longitudinal bias magnetic fields from the hard bias layers 8.
When an external magnetic field is applied to the magnetic detection element shown in FIG. 7, the magnetization direction of the free magnetic layer is varied relative to the magnetization direction of the pinned magnetic layer and, thereby, the resistance value of the laminated film is varied. In the case where a sense current is flowed with a constant current value, the external magnetic field is detected by detecting this variation of the resistance value as the variation of voltage.
The magnetic detection element including the free magnetic layer formed from the Heusler alloy is described in Japanese Unexamined Patent Application Publication No. 2003-218428 (US Pub. No. 2003/0137785 A1).
It is known that the product ΔRA of a variation of magnetoresistance ΔR and an element area A can be increased by forming the above-described free magnetic layer primarily from the Heusler alloy. An increase in the above-described ΔRA is one of very important conditions for commercializing a CPP type magnetic detection element directed toward a future increase in recording density.
Although the above-described ΔRA is increased by using the Heusler alloy, the magnetostriction of the free magnetic layer is increased. If the magnetostriction of the free magnetic layer is increased, an influence of stress is increased due to, for example, the film-formation strain and the difference in thermal expansion coefficient between the free magnetic layer and other layers. Furthermore, on the grounds that, for example, noise is caused during the operation of a head, another problem occurs in that the magnetostriction of the above-described free magnetic layer must be reduced while a high ΔRA is maintained.